Pressure-sensitive record material

ABSTRACT

Record material comprising paper sheet material coated with liquid-containing microcapsules wherein the liquid contents comprise isopropylbiphenyl and no halogenated hydrocarbon liquid. Said liquid is associated on the record material with at least two color-producing reactants, at least one of which is soluble in said liquid. The encapsulated liquid is associated with the reactants by either being in close proximity to both reactants or by having one of the reactants dissolved therein and being in close proximity to the other. Of the color-producing reactants, one is a chromogenic dye-precursor and one is a coreactant material capable of developing the color of the chromogenic dyeprecursor when the two reactants are brought into reaction contact by rupture of the capsule walls that contain said liquid.

United States Patent [111 3,627,581

[72] Inventor Paul S. Phillips, .Ir- 3,481,759 12/1969 Ostlie l 17/36.2 Dayton, Ohio 3,488,207 1/1970 Vassiliades. 1 17/36.2 [21] Appl. No. 82,198 3,540,913 11/1970 Lin 117/362 [22] Filed Oct. 19, 1970 [45] Patented Dec. 14, 1971 [73] Assignee The National Cash Register Company Primary Examiner-Murray Katz Attorneys- E. Frank McKinney and Edward McC. Roberts Dayton, Ohio ABSTRACT: Record material comprising paper sheet materi- [54] PRESSURESENSITIVE RECORD MATERIAL a] coated with liquid-containing microcapsules wherein the 14 Claims No Drawings tquld contents comprise lsopr opylblphenyl and no halogenated hydrocarbon liquid. Said llqLlld IS associated on [52] U.S.C1 117/362, the record material with at least two color-producing reac- 1 17/156, 252/316, 106/137 tants, at least one of which is soluble in said liquid. The encap- [51] Int. Cl. B4lm 5/16 sulated liquid is associated with the reactants by either being [50] Field of Search 117/362, in close proximity to both reactants or by having one of the 36.8, 36.9 reactants dissolved therein and being in close proximity to the other. Of the color-producing reactants, one is a chromogenic [56] Ree'ences cued dye-precursor and one is a coreactant material capable of UNITED STATES PATENTS developing the color of the chromogenic dye-precursor when 3,432,327 3/1969 Kan et a1 1 17/36.2 the feaciams are brought into reaction Contact by rupture of the capsule walls that contain said liquid.

PRESSURE-SENSITIVE RECORD MATERIAL There is provided by this invention record material, comprising paper sheets coated with isolated liquid droplets, comprising isopropylbiphenyl and no halogenated hydrocarbon liquid. Said isolated liquid droplets are associated on the record material with at least two color-producing reactants, at least one of which is soluble in said liquid. The liquid is associated with the reactants by either being in close proximity to both reactants or by having one of the reactants dissolved therein and being in close proximity to the other. Of the colorproducing reactants, one is a chromogenic dye-precursor and one is a coreactant material capable of developing the color of the chromogenic dye-precursor when the two reactants are brought into reaction contact by rupture of the isolating medium. lsolation of the liquid droplets is preferably accomplished by encapsulation of the droplets with polymeric film material.

In the art of making pressure-sensitive record material of the type described which includes liquid containing microcapsules, successful commercial embodiments have made use of Crystal Violet Lactone (hereinafter called CVL) as the chromogenic dye-precursor material, an acidic coreactant material such as attapulgite clay or an oil-soluble, para-substitued-phenoLaldehyde novolak resin, and a liquid solvent that is at least in part a halogenated aromatic liquid, particularly mixtures of chlorinated biphenyls. Halogenated aromatic liquids have low vapor pressure and good solvent power and are readily retained by gelatin films (the most widely used capsular wall material). The halogenated aromatics have therefore served well as the solvent in pressure-sensitive record material systems of the type described. However, it has now been found that the fade rate of so-made CVL prints on exposure to air and light is increased by the presence of halogencontaining solvents. A search for nonhalogenated solvents, having the advantages of chlorinated biphenyls without the disadvantage of accelerating print-fade has produced the aromatic solvent systems of this invention which include isopropylbiphenyl.

Amylbiphenyl, with impurities and isomer ratios unspecified, was disclosed as a vehicle for making colored pigment suspensions for use as an encapsulated marking liquid in a coated record sheet by Macauley in U.S. Pat. 3,016,308 which issued Jan. 9, 1962. Macauley in the same patent further disclosed a 111:1 mixture of chlorinated biphenylamylbiphenyl-amylnaphthalene as the solvent for methylviolet butyl ether, again for use as an encapsulated marking liquid in a coated record sheet. Amylbiphenyl as part of an encapsulated dye-precursor solvent system which does not also include halogenated aromatics has not, as far as is known, been taught in the art. However, amylbiphenyl was tested in the hope of its meeting the objects of this invention. Amylbiphenyl has not been found satisfactory in the record systems of this invention partly because of its low solubilizing power but mainly because of its perfonnance in use. Prints made on a standard commercial novolak-sensitized receiving sheet with a 2:1 amylbiphenyl-saturated hydrocarbon oil solution of CVL were much less intense than similarly made prints using a 2:1 chlorinated-biphenyl-saturated hydrocarbon oil solution of CVL. Furthermore, the CVL-in-amylbiphenyl prints faded even more rapidly and completely than the known-art CVL- in-chlorinated-biphenyl prints. The failure of amylbiphenyl to meet the objects of this invention and improve on the chlorinated aromatic solvents of the known art made even more surprising the advantageous performance of isopropylbiphenyl, the use of which is set out herein.

By isoproplybiphenyl is meant a compound or a mixture of compounds of the structure:

CH(CH3)2 The isopropyl group may be attached to the benzene ring at the ortho, meta or para positions. Synthetic methods commonly used produce a mixture of at least two of the three possible isopropylbiphenyls. Of particular use in this invention is the mixture wherein meta-isopropylbiphenyl and paraisopropylbiphenyl are the predominant isomers. These two isomers appear to perform in the record material systems of the invention equally well and whether alone or in combination to perform better than ortho-isopropylbiphenyl.

lsopropylbiphenyl has been found to give better print intensities and better fade resistance than higher alkylated biphenyls such as butylbiphenyl, amylbiphenyl, hexylbiphenyl, decylbiphenyl, diisopropylbiphenyl and triisopropylbiphenyl. Increasing alkyl content in the alkylated biphenyls also leads to generally poorer solubilizing properties at least when CVL is the chromogen to be dissolved. However, a certain amount of higher alkylated biphenyls as impurities in the isopropylbiphenyl can be tolerated. When the impurities are polyisopropylbiphenyls, that is generally diisopropylbiphenyl with trace amounts of triisopropylbiphenyl, no more than about 55 percent, by weight, of the total biaryl content should be such higher alkylated species. Preferably no more than about 25 to 30 percent of the total biaryl content is polysiopropylbiphenyl. Unalkylated biphenyl, that is biphenyl itself, can also be tolerated as an impurity in the isopropylbiphenyl. Biphenyl as an impurity does not noticeably hurt the performance of isopropylbiphenyl in the record materials of this invention, but when biphenyl makes up more than about 10 percent of the total biaryl content the biphenyl odor generally makes such record materials commercially unacceptable. By total biaryl content" is meant the amount of isopropylbiphenyl present, together with its impurities,

polyisopropylbiphenyl and biphenyl. By polyisopropylbiphenyl is meant biphenyl having two or more isopropyl s i ssvb itqts ths q Nonhalogenated diluent oils may be added to the isopropylbiphenyl without adversely affecting the performance of the record systems made therewith. High-boiling aliphatic hydrocarbons and C, -C,,,-alkylbenzenes have been used successfully as isopropylbiphenyl diluents. Since these diluents are generally cheaper than isopropylbiphenyl, their use is in the interest of economy. Solubility of the chosen colorless, chromogenic dye-precursor material in the chosen diluent dictates the maximum amount of such diluent which can be used. If the isopropylbiphenyl is to be diluted with other oils, the diluted isopropylbiphenyl should be capable of dissolving at least one percent and preferably 1.5 percent or more of the chosen dye-precursor. When CVL is the chosen dye-precursor, the preferred diluents are saturated aliphatic hydrocarbon oils (with a distillation range in the range of 320 to 550 F.), which may be added to isopropylbiphenyl to make up about one-third of the total weight of the CVL solvent, and C,,C, -alkylbenzene which may be used to the extent of two-thirds of the total weight of said solvent.

Of course, in addition to the preferred diluent hydrocarbon oils discussed above, many oils known to the art as useful internal phase solvents, may be used as a diluent herein for the isopropylbiphenyl provided they are not halogenated, are at least partially miscible with isopropylbiphenyl so as to give a single phase in the proportions used, and are not chemically reactive with isopropylbiphenyl or the other components of the marking liquid. For instance, low molecular weight aromatic hydrocarbons such as xylene and toluene, organic acid esters such as fatty acid esters and phthalic acid esters, phosphate esters such as dibutylphosphate, dioctyl phosphate and dicresylphosphate, and ethers such as diphenyl oxide are alleligible foruse as diluent oils. 7 V

An unexpected advantage of the record material of this invention (in addition to the previously recited increase in fade-' resistance) is that color-production efficiency is also enhanced over the known-art systems which include chlorinated biphenyls. This allows the use of less marking liquid per unit area to produce the same amount of color. The color-production efficiency of record material coated with microcapsules having an internal phase consisting of 1.7 percent CVL dissolved in a 2:1 mixture of isopropylbiphenyl and saturated hydrocarbon oil is 16 percent greater than the colorproduction efficiency of record material coated with microcapsules having an internal phase consisting of 1.5 percent CVL dissolved in a 2:1 mixture of a chlorinated biphenyl (of 42 percent chlorine content) and saturated hydrocarbon oil. This increased efficiency reprewnts a saving in rawmaterial costs as well as reduced coating weights on the finished product.

lsopropylbiphenyl solvent materials of the following compositions were tested and found to represent an improvement over chlorinated biphenyls:

TABLE I Percent composition (by weight) Sample Qrtho- Meta- Para- Polyisoprodesignation lsomer isomer isomer pylbiphenyl Biphenyl 65. 8 31. 4 0. 70 64. 8 34. 1 0. 10 21. 8 40. 1 1i. 6 0. 10 50. 5 29. 6 23. 6 0. 40 24. 5 I4. 5 54. 7 8. 70 23. 4 16.8 41. 5 14. 20 30. 6 17. 6 48. 9 0. 40 46.4 28. 3 24. 3 1. 10 21. 5 13. l 54. 2 8. 8O 46. 3 24. 9 21. 4 9. 50' 41. 0 23. 4 39. 8 0.70 46. 0 25. 1 22. 0 8. 80 49. 6 29. 1 23. 5 0. 60

The preferred composition for use in this invention is approximately 50 percent meta-isopropylbiphenyl, 30 percent para-isopropylbiphenyl, 25 percent polyisopropylbiphenyl, 0.5 percent biphenyl. This preferred composition is best represented by Samples D" and N," above.

Samples of isopropylbiphenyl having about 75 percent polyisopropylbiphenyl impurity associated with about 25 percent isopropylbiphenyl (a mixture of meta and para isomers) were found, when mixed 2:1 with a saturated hydrocarbon oil and used as the internal phase solvent for CVL, to give slightly less intense prints on phenolicresin sensitized paper than 2:1 chlorinated-biphenyksaturatcd hydrocarbon oil solutions of CVL did and to show no appreciable improvement in fade resistance.

Satisfactory isopropylbiphenyl for use herein may be obtained commercially or may be synthesized by Friedel-Crafts alltylation of biphenyl, a study of which reaction is reported in industrial and Engineering Chemistry Product Research and Development, 8 239-241 (1969), by Duane B. Priddy.

Dye-precursor materials in addition to CVL which may be dissolved in isopropylbiphenyl for encapsulation purposes include any colorless, chromogenic dye-precursor materials such as those disclosed in the U.S. application of Robert E. Miller and Paul S. Phillips, Jr., Ser. No. 44, 805, filed June 9, 1970.

The same Miller-Phillips application also discloses those phenol-aldehyde resins eligible for use as coreactant materials to develop the color of the dye-precursor materials. In general, the preferred resins are oil-soluble para-substitutedphenol-formaldehyde novolak resins.

Other useful phenolic resins are disclosed in U.S. application, Ser. No. 830,921, filed May 26, 1969 by Robert E. Miller and Bruce W. Brockett.

Capsule-wall materials and capsule manufacture are not critical to this invention. Suitable capsules may be made according to the procedures taught in U.S. Pat. Nos. 2,800,457 July 23, 1957), 2,800,458 (July 23, 1957) which became Re. 24,899 (Nov. 29, 1960) and 3,041,289 June 26, 1962). Other methods of isolating the marking droplets are also applicable here, such as entrapment of the droplets in a dried emulsion film.

annn

'dicated.

EXAMPLE 1 Encapsulation of CVL-isopropylbiphenyl Solution-A solution of CVL, 1.7 percent, in isopropylbiphenyl, Sample D"of Table l, was chosen for use as the internal phase of the capsules. The following formulation was emulsified in a Waring Blendor" at 55 C. to give internal phase droplets of 4 microns diameter:

150 grams of internal phase 150 grams of 10 percent gelatin at pH 6.5

62 grams of deionized water. Coacervation was accomplished by addition to the above emulsion, under continued agitation at 55 C., of grams of 10 percent gum arabic solution, 10 grams of 5 percent PVM/MA, po1y(vinyl methyl ether/maleic anhydride) and 600 grams of deionized water. With continued agitation and temperature maintenance, the mixture was treated with sufficient 20 percent sodium hydroxide solution to adjust the pH to 9.0 and then with 12.5 milliliters of 14 percent acetic acid, dropwise. The mixture was then cooled slowly, with continued agitation, to 12 C. and treated with 7.5 milliliters of 25 percent glutaraldehyde. After 4 hours of stirring, 12.0 milliliters of basic 5 percent PVM/MA (pH 9.0) is added, dropwise, to the mixture which is then stirred for an additional 2.5 hours while it gradually warms, up to about room temperature. The pH of the mixture, which is now a suspension of microcapsules, was finally adjusted to 9.5 with 20 percent sodium hydroxide. The microcapsulcs may be used as is, as an aqueous suspension or they may be isolated by filtration and airdried.

EXAMPLE 2 Encapsulation of CVL-isopropylbiphenyl-hydrocarbon oil. According to the procedure of Example 1, microcapsules were made wherein a 2:1 mixture of isopropylbiphenyl and a saturated hydrocarbon oil (distillation range 370-500 F.) was substituted for the isopropylbiphenyl of that example.

EXAMPLE 3 Encapsulation of CVL-isopropylbiphenyl-alkylbenzene.According to the procedure of example 1, microcapsules were made wherein a 1:2 mixture of isopropylbiphenyl and a mono-C to C -alkylbenzene was substituted for the isopropylbiphenyl of that example.

EXAMPLE 4 Encapsulation of phenolic resin solution.-Gcnerally follow ing the method of example 1, a 10 percent solution of paraphenylphenolformaldchyde novolak resin in a 2:1 mixture of isopropylbiphenyl and xylene was encapsulated. The initial emulsion consisted of 180 grams of internal phase, 191 grams of 11 percent gelatin at pH 4.3 and 15.8 grams of deionized water. Coacervation was accomplished by the addition of 127 grams of 1 1 percent gum arabic solution, grams of 5 percent PVM/MA and 817 grams of deionized water. In the final stages, 21 milliliters of 14 percent acetic acid, 10 milliliters of 25 percent glutaraldehyde, and 20 milliliters of basic 5 percent lVM/MA were added instead of the amounts specified in example 1. The final stirring times were also changed: 16 hours following the glutaraldehyde addition and one hour following the final basic PVM/MA addition. The final adjustment of the pH to 9.5 was omitted.

EXAMPLE 5 Capsule-Coated Record Material Sheets.--An aqueous coating slurry of the following composition was made up by stir- Water Paper sheets were coated with the above slurry with a No. Mayer rod to give a dried coating weight of about 3.5 pounds per ream (500 sheets, measuring 25x38 inches).

Coatings made with the capsules of examples I, 2 or 3 gave record material sheets that yielded intense blue marks when marked on against acid-sensitized receiving sheets. The test receiving sheets were standard commercial receiving sheets sensitized according to the teaching of the previously cited Miller-Brockett application. The so-produced marks were more intense and more fade resistant (when exposed to light and air) than similar marks made with coated sheets having 2:1 chlorinated biphenyl-hydrocarbon oil as the capsular internal phase solvent for the CVL.

Similar results were observed when the coated sheets bearing the capsules of example 4 were used as the transfer sheet against a facing receiving sheet that had been sensitized by being dipped in an acetone solution of a colorless, chromogenic, dye-precursor and dried. Among the colorless, chromogenic, dye-precursor materials used in this test were CVL, Malachite Green Lactone, N-(2,5-dichlorophenyl) leucauramine, N-benzoylauramine, Methyl Red, 4- aminoazobenzene, 8-methoxybenzoindolinospiropyran and Rhodamine B Lactam.

What is claimed is:

1. Record sheet material comprising isolated droplets of an oil solution of a color-producing reactant material, selected from the group consisting of base-reacting colorless chromogenic dye-precursor materials and acid-reacting phenol-formaldehyde novolak resins capable of producing color in said dye-precursors when brought into reactive contact therewith, wherein said oil is a halogen-free oil comprising biaryl material selected from the group consisting of biphenyl. isopropylbiphenyl and polyisopropylbiphenyl with the requirement that of the total biaryl content at least 30 percent must be isopropylbiphenyl, not more than 55 percent may be polyisopropylbiphenyl, and not more than 15 percent may be biphenyl.

2. The record sheet material of claim I wherein the isopropylbiphenyl is a mixture of the isomers, meta-isopropylbipheny] and para-isopropylbiphenyl.

3. The record sheet material of claim 2 wherein the metapara isomer ratio is about 5:3.

4. The record sheet material of claim 1 wherein the oil further comprises a high-boiling saturated aliphatic hydrocarbon oil.

5. The record sheet material of claim 4 wherein the biarylsaturated aliphatic hydrocarbon oil ration is about 2:1.

6. The record sheet material of claim 4 wherein the saturated hydrocarbon oil has a distillation range in the range of 320 to 550 F.

7. The record sheet material of claim 1 wherein the oil further comprises mono-C to C, -,-alkylbenzene.

8. The record sheet material of claim 7 wherein the alkylbenzene is mono-C to C -alkylbenzene.

9. The record sheet material of claim 7 wherein the biarylalkylbenzene ratio is in the range 2:1 to 1:2.

10. The record sheet material of claim 1 wherein the colorproducing reactant material is Crystal Violet Lactone.

11. The record sheet material of claim 1 wherein the colorproducing reactant material is para-substituted-phenol novolak resin.

12. The record sheet material of claim 11 wherein the novolak resin is para-phenylphenol-formaldehyde resin.

13. The record sheet material of claim 1 wherein the total biaryl content consists of about percent of a mixture metaisopropylbiphenyl and para-isopropylbiphenyl, about 20 percent of polyisopropylbiphenyl, and about l percent biphenyl.

14. The record sheet material of claim 1 wherein the isopropylbiphenyl is predominantly meta-isopropylbiphenal.

I l l t l UNITED STATES PATENT GFFICE CERTIFICATE OF CORRECTTUN Patent N 3 Dated December 14:,

Inventor-( PAUL S. PHILLIPS, JR.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 32: "paura-substicuted phenol should be -parasub stituted-phenol-form aldehyde Column 6, line 41: "meta-isopropylbiphenal" should be --meta-isopropy1bipheny1--.

' Signed and sealed this 13th day of March 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. I ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF Patent NO- 3, Dat d December 14;,

It is certified that error appears in the above-identified patent and that said Letters Patent: are hereby corrected as shown below:

Column 6, line 32: "para-substituted-phenol" should be -parasub stituted-phenol-form aldehyde Column 6, line 41: "meta-isopropylbiphenal" should be -metaisopropy1bipheny1-.

Signed and sealed this 13th day of March 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. The record sheet material of claim 1 wherein the isopropylbiphenyl is a mixture of the isomers, meta-isopropylbiphenyl and para-isopropylbiphenyl.
 3. The record sheet material of claim 2 wherein the meta-para isomer ratio is about 5:3.
 4. The record sheet material of claim 1 wherein the oil further comprises a high-boiling saturated aliphatic hydrocarbon oil.
 5. The record sheet material of claim 4 wherein the biarylsaturated aliphatic hydrocarbon oil ratio is about 2:1.
 6. The record sheet material of claim 4 wherein the saturated hydrocarbon oil has a distillation range in the range of 320* to 550* Fahrenheit.
 7. The record sheet material of claim 1 wherein the oil further comprises mono-C10 to C15-alkylbenzene.
 8. The record sheet material of claim 7 wherein the alkylbenzene is mono-C11 to C12-alkylbenzene.
 9. The record sheet material of claim 7 wherein the biarylalkylbenzene ratio is in the range 2:1 to 1:2.
 10. The record sheet material of claim 1 wherein the color-producing reactant material is Crystal Violet Lactone.
 11. The record sheet material of claim 1 wherein the color-producing reactant material is para-substituted-phenol -formaldehyde novolak resin.
 12. The record sheet material of claim 11 wherein the novolak resin is para-phenylphenol-formaldehyde resin.
 13. The record sheet material of claim 1 wherein the total biaryl content consists of about 80 percent of a mixture meta-isopropylbiphenyl and para-isopropylbiphenyl, about 20 percent of polyisopropylbiphenyl, and about 1 percent biphenyl.
 14. The record sheet material of claim 1 wherein the isopropylbiphenyl is predominantly meta-isopropylbiphenal. 